Detection of Highly Pathogenic Avian Influenza in 

Dairy Herds: Frequently Asked Questions

As of Friday, March 29, USDA’s Animal and Plant Health 

Inspection Service (APHIS) has confirmed the detection of 

highly pathogenic avian influenza (HPAI) in dairy herds in 

Texas, Kansas, and Michigan. APHIS’ latest update on the HPAI 

detections can be found in this press release. 

APHIS is also investigating possible connections to other 

herds with cows exhibiting similar signs of illness, including 

additional herds in New Mexico, Texas, and Idaho. This 

is a rapidly evolving situation and USDA, as well as state 

and federal partners, are committed to sharing updates 

as information becomes available. Here, we are answering 

some of the most frequently asked questions about these 

detections. 

How did these cattle contract HPAI?

Wild migratory birds are believed to be the source of infection. 

However, the spread of the illness among the Michigan herd 

also indicates that HPAI transmission between cattle cannot be 

ruled out. 

Initial testing has not found changes to the virus that would 

make it more transmissible to humans. While cases among 

humans in direct contact with infected animals are possible, 

this indicates that the current risk to the public remains low.

Is this the same strain that has been in circulation among 

wild and commercial flocks in recent months, or is this a 

different strain? 

Tests so far indicate that the HPAI detected in dairy cows is 

H5N1, Eurasian lineage goose/Guangdong clade 2.3.4.4b. This 

is the same strain and clade that has been affecting wild birds 

and commercial poultry flocks and has been detected in some 

wild animals. 

How is a case of HPAI in cattle confirmed by USDA?

USDA encourages producers to work with their veterinarians 

to report cases of sick cattle to State Animal Health Officials 

and their APHIS Veterinary Services Area Veterinarian in 

Charge. Veterinarians should submit samples to a National 

Animal Health Laboratory Network (NAHLN) laboratory for 

initial testing. Samples with non-negative test results are then 

submitted to the National Veterinary Service Laboratories 

www.aphis.usda.gov/animalhealth

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APHIS 24-020 | March 2024

(NVSL) in Ames, Iowa for confirmatory testing. USDA considers 

a positive test result from NVSL tests as confirmation, and 

NVSL carries out viral genome sequencing, as needed. 

What types of samples from cows have been tested? 

USDA and our NAHLN partner laboratories have tested 

unpasteurized, clinical samples of milk, swabs and tissue 

samples collected from sick cattle. 

Should we assume that other cattle that are showing 

similar symptoms, including decreased lactation, have 

also contracted HPAI?

We encourage producers to work with their veterinarians to 

pursue testing if their herds are demonstrating clinical signs 

of the current cattle illness event. Federal and state agencies 

continue to test samples from sick animals and conduct 

viral genome sequencing, to assess whether HPAI or another 

unrelated disease may be part of the clinical picture.

Combined with the recent detections of HPAI in baby 

goats in Minnesota, is there reason to be concerned HPAI 

may spread to mammals more commonly than previously 

believed? 

HPAI has been found in wild birds, poultry flocks, several 

species of wild mammals, and neonatal goats in the United 

States. A full list can be found here. Many species are 

susceptible to influenza viruses, including wildlife that often 

come into direct contact with wild birds. Many of these animals 

were likely infected after consuming or coming into contact 

with birds that were infected with HPAI. In the case of the 

neonatal goats in Minnesota, they were exposed to domestic 

birds (ducks and chickens) infected with HPAI through shared 

pasture and a sole water source. However, recent testing 

indicates that HPAI transmission between cattle cannot be 

ruled out.

Why is USDA recommending caution when moving cattle? 

And, has the department considered requiring movement 

restrictions? 

The spread of the HPAI within the Michigan herd indicates 

that bovine to bovine spread cannot be ruled out. As a result, 
we are encouraging producers and veterinarians to minimize 

dairy cattle movement. At this time, we expect that minimizing 

movement, upholding good biosecurity practices, and testing 

animals before necessary movements will limit disease spread 

sufficiently to avoid the need for regulatory restrictions or 

quarantines. Unlike in poultry flocks where HPAI is fatal, 

among the dairies whose herds are exhibiting symptoms, the 

affected animals have recovered with little to no associated 

mortality reported. 

How is this cattle illness affecting the nation’s overall milk 

production? What effect might this have on consumer 

prices?

At this point, we are not aware of impact on milk supply or 

consumer prices. Based on information available at this point, 

we do not anticipate that this will impact the availability 

or the price of milk or other dairy products for consumers. 

In addition, the U.S. typically has a more than sufficient 

milk supply in the spring months due to seasonally higher 

production. Markets continue to reflect normal movements. 

Surplus loads of milk for the past week are selling significantly 

below market value indicating supply remains very long.

What are the latest trends in HPAI detections and virus 

mitigation?

Recent detections of HPAI in poultry have slowed. So far in 

2024, there have been 21 detections of HPAI in commercial 

poultry facilities, which is similar to the number in JanuaryMarch of 2023 (17 detections). Both years are showing 

significant decreases in the number of detections compared 

to 2022, when we saw 59 detections in the January-March 

period, indicating that biosecurity practices and virus 

management have played a significant role in reducing impacts 

to commercial flocks. 

What is the species of deceased wild birds that were found 

on the Texas farms?

At this time, three species have been identified among these 

cases: pigeons, blackbirds, and grackles.

Will the HPAI detection require herds to be depopulated, as 

is the case with detections in poultry flocks?

At this stage, we do not anticipate the need to depopulate 

dairy herds. Unlike HPAI in birds which is typically fatal, little to 

no mortality has been reported and the animals are reportedly 

recovering. The affected cows on the dairy farms are currently 

being isolated from other animals. We are continuing to learn 

more about the situation. Transparency and collaboration with 

and by dairy producers will be important to mitigate broader 

potential impacts to the industry.

Has this impacted beef cattle or the beef supply?

USDA is confident that the meat supply is safe. As always, we 

encourage consumers to properly handle raw meats and to 

cook to a safe internal temperature. Cooking to a safe internal 

temperature kills bacteria and viruses, like influenza, in meat.

How can farmers prevent the spread of HPAI to their 

animals?

It is critically important that farmers practice good biosecurity 

measures. We are also encouraging producers with concerns 

to reach out to their veterinarian, State Animal Health Official, 

and/or Area Veterinarian in Charge. 

If an animal is displaying signs of illness or tests positive for 

HPAI, the animal should be separated from other animals 

on the farm and heightened biosecurity measures should 

be taken to ensure HPAI does not spread to other species. 

Additionally, farmers are advised to avoid housing multiple 

species of animals together at any time. 

More specific information on biosecurity practices are 

available:

 Specific to dairy herds; 

 Specific to poultry flocks; and

 General influenza biosecurity.

What signs of illness should farmers look out for in their 

herds? 

Producers should report animals with the following clinical 

signs to their state veterinarian immediately:

Decreased herd level milk production; acute sudden drop in 

production with some severely impacted cows experiencing 

thicker, concentrated, colostrum-like milk; decrease in feed 

consumption with a simultaneous drop in rumen motility; 

abnormal tacky or loose feces, lethargy, dehydration, and 

fever. Initial cases indicated older cows in mid-lactation may 

be more likely to be severely impacted than younger cows and 

fresh cows or heifers. Additional data indicates younger cattle 

have been affected; more data and reporting from impacted 

producers will help to clarify the range of animals affected. 

Will there be a milk recall? 

Based on the information and research available to us at this 

time, a milk recall is not necessary. Because products are 

pasteurized before entering the market, there is no concern 

about the safety of the commercial milk supply, or that this 

circumstance poses a risk to consumer health. Pasteurization 

has continuously proven to inactivate bacteria and viruses, like 

influenza, in milk. 

Could the consumption of raw milk from these states 

impact human health? 

FDA’s longstanding position is that unpasteurized, raw milk 

can harbor dangerous microorganisms that can pose serious 

health risks to consumers, and FDA is reminding consumers of 

the risks associated with raw milk consumption in light of the 

HPAI detections. Food safety information from FDA, including 

information about the sale and consumption of raw milk, can 

be found here.